In an electrophotographic printing machine, a photoconductive member is charged to a substantially uniform potential to sensitize the surface thereof. The charged portion of the photoconductive member is image-wise exposed. Exposure of the charged photoconductive member selectively dissipates the charge thereon in the irradiated areas. As a result, an electrostatic latent image is recorded on the photoconductive member corresponding to the informational areas contained in the original document being reproduced. After the electrostatic latent image has been recorded on the photoconductive member, the latent image is developed by bringing toner into contact therewith. This forms a developed toner image on the photoconductive member which is subsequently transferred to a copy sheet. The copy sheet is heated to permanently affix the toner image thereto in image configuration.
Multicolour electrophotographic printing is substantially identical to black-and-white printing. However, rather than forming a single latent image on the photoconductive surface, successive latent images corresponding to different colours are recorded thereon. Each single colour electrostatic latent image is developed with toner of a colour complementary thereto. This process is repeated a plurality of cycles for differently coloured images and their respective complementarily coloured toner. Each single colour toner image is transferred to the copy sheet in superimposed registration with the prior toner image, thereby creating a multilayered toner image on the copy sheet. Thereafter, the multi-layered toner image is permanently fixed to the receptor sheet creating a colour copy or print. The developer material may be a liquid material or a powder material.
In order to successfully transfer different colour toner images to the copy sheet, the sheet can move in a path enabling successive different colour images to be transferred thereto. In this way the different colour toner images (e.g. magenta, cyan, yellow and black toner images) are transferred to the sheet.
One known technique for carrying out the described process comprises the use of an endless photoconductive belt onto which the distinct separation toner images are formed in succession, and from which these images are transferred in timed relation in coinciding relationship onto a receptor sheet to obtain a multilayered toner image.
The movement of suchlike endless photoconductive belt is a delicate point, since it must meet high standards of reproducibility and uniformity in order to obtain a desired image quality.
It is the aim of the present invention to provide an electrostatographic printing apparatus with a recording member in the form of an endless belt, such endless belt being guided along an endless path by air bearings providing an improved belt guidance.